Apple just announced the iPhones 5S featuring the A7 SoC, which is the world's first consumer ARM based SoC with 64-bit support. We're likely talking about an updated version of Apple's Swift microprocessor with ARMv8 support.

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You could argue doubling of registers has nothing to do with 64 bit, had someone was building this processor from ground-up, but that's not the case here. ARM v8 ISA doubles the number of registers, and ARM v8 is 64 bit ISA, so doubling up registers would have been not possible without moving to 64 bit. Plus, there are other improvements ARM made to v8 over v7, so this argument of 64 bit "just preparing for larger memory" is really a huge overgeneralization, because the implementation of ARM v8 architecture, not just 64 bit, should provide performance improvement in many areas, just like how ARM's own A57 design generally performs better all around than A15 (they have similar pipeline, but A57 is v8 architecture whereas A15 is v7).Reply

Your logic would be correct if a 64-bit ISA were the only way to execute instructions on 64-bit or larger data types, but that is not at all the case with the ARM v7/v8 ISA's. With Neon and VFPv4 extensions, the ARMv7 (32-bit ISA) is very capable of doing 64-bit data operations (http://infocenter.arm.com/help/index.jsp?topic=/co... Sure, 64-bit ISA's typically give you 64-bit general purpose registers (and 32-bit ISA's typically limit you to 32-bit general purpose registers), but those aren't the primary determinant of performance in throughput dominated workloads (implied by your comment about "available resources / performance of the pipeline"). FP/NEON registers are the limiting factor in this case, and ARM v7 (a 32-bit ISA) supports up to 64-bit registers in that domain.Reply

64Bit can related to either the address bus, the data bus or a set of registers. Typically the old description of the Bit was the address bus, relating to how much memory a system could address. This is not the case anymore as 64Bit mainly relates to the size of the general purposes registers, not the amount of RAM that is addressable. Reply

Actually there's no need to have that much memory on iOS devices because it's far more memory efficient than either Windows Phone 8, BB10, Windows RT or Android. They won't put 4GB of memory on an iPad for a long time, maybe the next version will have 2GB if they find a sufficient use case for that but I'm sort of thinking not.Reply